What Am I Riddles

Question: When you bend me I'm kind
But I'm very hard to find
I'm easily sold
and rhyme with this when told

What am I?

Question: I support the fallen (ones) I restrain the naughty (ones) I replace the nonexistent (ones) What am I?

Question: I am a big threat to humanity,
but you wouldn't get rid of me even if you could.

What am I?

Question: I go into the water red and come out black.

What am I?

Question: I give advice to others,
yet I know nothing myself.
I am a hitchhiker destined to stay still.